From: Joel VanderWerf <vjoel@...>
Date: 2008-01-04T10:45:53+09:00
Subject: Re: Finding if an array contains a data type

Sam Phoneix wrote:
> Say I wanted to see if an array contained a number or not. Would I use
> the match method?
> 
> E.g.
> 
> x=["a","b",2, "c"]
> 
> puts("This array contains numbers") if x.match(/\d/)

Another way, just for fun:

x=["a","b",2, "c"]
puts("This array contains numbers") unless x.grep(Numeric).empty?

Let's take apart what that means:

1. The Enumerable#grep method uses the "matching" operator === to search 
for all matches to the argument, which are collected into a new array.

2. In this case, grep's argument is a class, so each element of x is 
matched using the following condition: Numeric === the_element.

3. When called on classes, === checks if the given object is a member of 
the class (or a descendent) or not.

But this is not the most efficient solution since it has to pass over 
the entire collection (instead of stopping on the first match), and it 
makes a new array with the results. It's really only useful when you 
need all matches, for some reason. Otherwise, follow the suggestion to 
use #any? and #is_a? or #kind_of?.

References:

ri Module#===
ri Enumerable#grep

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407